docs: def assert_not_equal(first, second, msg_fmt="{msg}"):
      """Fail if first equals second, as determined by the '==' operator.
  
      >>> assert_not_equal(5, 8)
      >>> assert_not_equal(-7, -7.0)
      Traceback (most recent call last):
          ...
      AssertionError: -7 == -7.0
  
      The following msg_fmt arguments are supported:
      * msg - the default error message
      * first - the first argument
      * second - the second argument
      """
  
      if first == second:
          msg = "{!r} == {!r}".format(first, second)
          fail(msg_fmt.format(msg=msg, first=first, second=second))